Oprah Winfrey on Wednesday spoke at the 50th anniversary of the March on Washington, telling the crowd to honor Martin Luther King Jr.’s dream and “be courageous by continuing to walk in the footsteps of the path that he forged.”

Three presidents, civil rights leaders, celebrities and thousands of people are set to descend on the National Mall to mark the 50th anniversary of Dr. Martin Luther King, Jr.’s revolutionary “I Have a Dream” speech. See the full schedule of speakers here.